Typically, refrigerated display cases with multi-pane glass assemblies require supplemental heat to prevent the formation of condensation on an outer pane of the multi-pane glass assembly. Supplemental heat is commonly supplied to the surface and/or perimeter of the glass panes. As a result, the overall energy consumption of the refrigerated display case is increased.
FIGS. 1 and 2 illustrate prior art glass assemblies 11, 51 for refrigerated display cases 10, 50. FIG. 1 shows a refrigerated display case 10 having a glass assembly 11 coupled to an insulated wall 12 with an extruded member 14. The glass assembly 11 includes a first pane of glass 16 having a first edge 18, a second pane of glass 20 having a second edge 22, and a third pane of glass 24 having an outer surface 25 and a third edge 26. The second pane 20 is separated from the first pane 16 to define a first air space 17, and the second pane 20 is separated from the third pane 24 by a second air space 19. A first spacer 28 is positioned within the first air space 17 adjacent the first and second edges 18, 22, and a second spacer 30 is positioned within the second air space 19 adjacent the second and third edges 22, 26. The first edge 18, the second edge 22 and the third edge 26 are all substantially aligned to form a perimeter edge 31 of the glass assembly 11.
The extruded member 14 is constructed of plastic and/or aluminum and includes a first portion 32 that engages the insulated wall 12, and a second portion 34 that engages the glass assembly 11 to couple the glass assembly 11 to an outer edge 36 of the insulated wall 12. The insulated wall 12 has a thickness X ranging from about 1.5 inches to about 2 inches. The glass assembly 11 has a thickness Y ranging from about 1.0 inches to about 1.5 inches. The glass assembly 11 is spaced a distance from the first portion 32 of the extruded member 14 to define a perimeter space 38 between the glass assembly 11 and the extruded member 14.
The third pane 24 is positioned adjacent the environment, and the first pane 16 is positioned adjacent a low temperature interior of the refrigerated display case 10. As a result, a highly-conductive heat transfer path P1 is defined through the glass assembly 11 by the first pane 16, the first spacer 28, the second pane 20, the second spacer 30, and the third pane 24. Specifically, heat is conducted from the environment through the third pane 24, the second spacer 30, the second pane 20, the first spacer 28, and the first pane 16 in a substantially linear path through the glass assembly 11 (i.e., from left to right in FIG. 1). As a result, condensation forms on the outer surface 25 of third pane 24 and/or an outwardly-facing portion of the extruded member 14 adjacent the third edge 26 of the third pane 24. A perimeter heater 40 is positioned in the perimeter space 38 between the glass assembly 11 and the extruded member 14 to counteract the results of the heat transfer path P1 through the glass assembly 11 and minimize the amount of condensation that forms on the outer surface 25 of the third pane 24 and/or the extruded member 14.
FIG. 2 shows another prior art refrigerated display case 50 having a glass assembly 51 positioned within a recess 53 of an insulated wall 52 of the refrigerated display case 50. The glass assembly 51 shown in FIG. 2 is coupled to the recess 53 with an extruded member 54.
The glass assembly includes a first pane 56 having a first edge 58, a second pane 60 having a second edge 62, and a third pane 64 having an outer surface 65 and a third edge 66. The second pane 60 is separated from the first pane 56 to define a first air space 57, and the second pane 60 is separated from the third pane 64 by a second air space 59. A first spacer 68 is positioned within the first air space 57 adjacent the first and second edges 58, 62, and a second spacer 70 is positioned within the second air space 59 adjacent the second and third edges 62, 66. The first edge 58, the second edge 62 and the third edge 66 are all substantially aligned to form a perimeter edge 71 of the glass assembly 51. The perimeter edge 71 of the glass assembly 51 is positioned within the recess 53 adjacent a bottom 73 of the recess 53 when the glass assembly 51 is installed in the insulated wall 52.
The third pane 64 is positioned adjacent the environment, and the first pane 56 is positioned adjacent a low temperature interior of the refrigerated display case 50. A conductive heat transfer path P2 is formed by the first pane 56, the first spacer 68, the second pane 60, the third spacer 70 and the third pane 64. However, the heat transfer path P2 is substantially embedded within the insulated wall 52. The glass assembly 51 has a thickness Y′ ranging from about 1.0 inches to about 1.5 inches. To provide adequate strength, support and insulation to the glass assembly 51, the insulation wall 52 has a thickness X′ greater than that required for prior art refrigerated display cases, such as the prior art refrigerated display case 10 illustrated in FIG. 1. Particularly, the thickness X′ is greater than 2 inches. Provided the thickness X′ of the insulated wall 52 is thick enough to properly insulate the elements that define the heat transfer path P2 from the environment, condensation should not form on the outer surface 65 of the third pane 64, and supplemental heat should not be required to be supplied to the third pane 64.